Latching mechanisms comprise on the one hand a switching mechanism for opening and closing a switch contact which is in operative contact with a tensioning element, and on the other hand an unlatching mechanism by which, in response to a tripping signal, the tensioning element can be transferred from a tensioned state into an at least substantially relaxed state in order in this way to open the switch contact.
Circuit breakers are special switches which are usually designed for high currents. These switches are not only able to switch operating currents and low overload currents, but in the event of errors can also switch on high overload currents and short-circuit currents, hold these fault currents for a predetermined time and switch them off again. Depending on embodiment variant, circuit breakers are implemented as single-pole or multi-pole.
Circuit breakers generally comprise so-called latching mechanisms which, when unwanted operating states occur, in particular in the case of short circuits, cause an electric circuit to be disconnected.
A latching mechanism is a mechanical apparatus which preferably enables an electric circuit to be disconnected. Toward that end the force of a tensioned spring which was tensioned by means of a tensioning mechanism at the time of switching on is usually released in order to open the switch contact. The typical tripping criterion is a current with a presettable current intensity by means of which the latching mechanism action is tripped with the aid of an electromagnet or of a self-heating bimetallic strip.
A circuit breaker latching mechanism comprises two essential areas. On the one hand, a switching mechanism is provided by way of which an electrical switch contact is opened and closed upon exposure to spring force. On the other hand, a latching mechanism of said kind comprises an unlatching mechanism which, when a tripping criterion is fulfilled, releases the energy stored in a spring of the switching mechanism, as a result of which the latching mechanism is tripped and the electrical switch contact is opened.
In this connection, solutions are known from the prior art which are intended to prevent the latching mechanism being tripped in the OFF position. Thus, for example, DE 693 06 822 T2 describes a circuit breaker latching mechanism comprising a so-called test button, the actuation of which ensures that the latching mechanism also does not trip in the OFF position. To this end, in the OFF position of the latching mechanism, the tensioning bolt mounted in the actuating lever slides onto a blocking contour on the tension lever, so that the latter is locked and in no event releases the latching mechanism or the switch. This makes it possible to press the test button and then actuate the tripping shaft without the latching mechanism being tripped. In this way the switching mechanism is kept in a pretensioned state even in the case of unintentional tripping.